[en] An overview of our recent work on the mechanisms of singlet and triplet exciton formation in electroluminescent -conjugated materials will be presented. According to simple spin statistics, only one-fourth of the excitons are formed as singlets. However, deviations from that statistics can occur if the initially formed triplet charge-transfer (CT) excited states are amenable to intersystem crossing or dissociation. Although the electronic couplings between the CT states and the neutral exciton states are expected to be largest for the lowest singlet and triplet excitons (S1 and T1, respectively), the possibility for direct recombination into T1 is always very small due to the large exchange energy. In small molecules, spin statistics is expected to be observed because both singlet and triplet exciton formations proceed via higher-lying Sn/Tn states with similar electronic couplings and fast formation rates. In extended conjugated chains, however, that the 1CT S1 pathway is faster while the 3CT Tn channels become much slower, opening the route to intersystem crossing or dissociation among the 3CT states.
Disciplines :
Physics
Author, co-author :
Beljonne, David ; Université de Mons > Faculté des Sciences > Chimie des matériaux nouveaux
Shuai, Z.
Ye, A.
Brédas, Jean-Luc ; Université de Mons > Faculté des Sciences > Chimie des matériaux nouveaux
Language :
English
Title :
Charge-Recombination Processes in Oligomer- and Polymer-Based Light-Emitting Diodes: A Molecular Picture
Publication date :
01 May 2005
Journal title :
Journal of the Society for Information Display
ISSN :
1071-0922
Publisher :
Wiley-Blackwell, United States
Volume :
13
Issue :
5
Pages :
419-427
Peer reviewed :
Peer Reviewed verified by ORBi
Research unit :
S817 - Chimie des matériaux nouveaux
Research institute :
R400 - Institut de Recherche en Science et Ingénierie des Matériaux
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